That may sound like a joke told by your five-year-old kid, but that's
what astronomers discovered:

A study led by a University of Utah astrophysicist found a new
explanation for the growth of supermassive black holes in the center
of most galaxies: they repeatedly capture and swallow single stars from
pairs of stars that wander too close.

Using new calculations and previous observations of our own Milky
Way and other galaxies, “we found black holes grow enormously
as a result of sucking in captured binary star partners,” says
physics and astronomy Professor Ben Bromley, lead author of the study,
which is set for online publication April 2 in Astrophysical Journal
Letters.

“I believe this has got to be the dominant method for growing
supermassive black holes,” he adds. “There are two ways
to grow a supermassive black hole: with gas clouds and with stars. Sometimes
there’s gas and sometimes there is not. We know that from observations
of other galaxies. But there are always stars.”